Abstract Background Thrombocytopenia is often considered a risk factor for bleeding, but conversely may be associated with an increased thrombotic risk in several clinical situations. Here we present a patient with arterial thrombosis and chronic disseminated intravascular coagulation caused by metastatic urothelial carcinoma. As the treatment for a disseminated intravascular coagulation caused by a neoplasia is the treatment of the underlying disease itself, our case highlights a new therapeutic approach—immunotherapy—in a patient prone to hematological complications due to conventional chemotherapy. Clinical case A 74-year-old Caucasian male patient with a history of urothelial carcinoma of the bladder and moderate thrombocytopenia had multiple arterial thrombotic events despite antiplatelet therapy and anticoagulation. A diagnosis of chronic disseminated intravascular coagulation in the setting of a metastatic bladder urothelial carcinoma was made. The patient was treated with an anti-PD-L1 monoclonal antibody, and achieved a rapid response with subsequent reversal of the disseminated intravascular coagulation. Conclusion Unexplained arterial or venous thrombosis despite adequate thromboprophylaxis should be investigated, especially in the setting of thrombocytopenia. Chronic disseminated intravascular coagulation is a possible, life-threatening reason for this clinical picture, and should prompt rapid identification of the underlying disease. To the best of our knowledge, this is the second case of chronic disseminated intravascular coagulation due to neoplastic disease treated with immunotherapy.